Conductance of mesoscopic systems with magnetic impurities

Vavilov, Maxim; Glazman, L. I.

doi:10.1103/physrevb.67.115310

Cited by 57 publications

(116 citation statements)

References 35 publications

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“…A complete derivation of the magnetic field dependence of ∆G h/e from first principles was finally published recently by Vavilov and Glazman. 47 As discussed in Section VII, the VavilovGlazman crossover function for S = 1/2 is nearly indistinguishable from ours.…”

Section: Appendix C: Magnetic Field Dependence Of Spin-flip Scatmentioning

confidence: 57%

“…Note that a more rigorous approach to the magnetic-field dependence of AB oscillation amplitude has been published recently by Vavilov and Glazman. 47 Using their prediction (Eqs. (62) and (63) in 47 ) with a magnetic impurity spin 48 S = 1/2 and g = 0.90, we ob-tain a fit indistinguishable from the solid lines calculated with the simple model.…”

Section: Test Of the Magnetic Impurity Hypothesis: Probing τ φ (B)mentioning

confidence: 99%

“…47 Using their prediction (Eqs. (62) and (63) in 47 ) with a magnetic impurity spin 48 S = 1/2 and g = 0.90, we ob-tain a fit indistinguishable from the solid lines calculated with the simple model.…”

Section: Test Of the Magnetic Impurity Hypothesis: Probing τ φ (B)mentioning

confidence: 99%

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Dephasing of electrons in mesoscopic metal wires

et al. 2003

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We have extracted the phase coherence time τ φ of electronic quasiparticles from the low field magnetoresistance of weakly disordered wires made of silver, copper and gold. In samples fabricated using our purest silver and gold sources, τ φ increases as T −2/3 when the temperature T is reduced, as predicted by the theory of electron-electron interactions in diffusive wires. In contrast, samples made of a silver source material of lesser purity or of copper exhibit an apparent saturation of τ φ starting between 0.1 and 1 K down to our base temperature of 40 mK. By implanting manganese impurities in silver wires, we show that even a minute concentration of magnetic impurities having a small Kondo temperature can lead to a quasi saturation of τ φ over a broad temperature range, while the resistance increase expected from the Kondo effect remains hidden by a large background. We also measured the conductance of Aharonov-Bohm rings fabricated using a very pure copper source and found that the amplitude of the h/e conductance oscillations increases strongly with magnetic field. This set of experiments suggests that the frequently observed "saturation" of τ φ in weakly disordered metallic thin films can be attributed to spin-flip scattering from extremely dilute magnetic impurities, at a level undetectable by other means. I. MOTIVATIONSThe time τ φ during which the quantum coherence of an electron is maintained is of fundamental importance in mesoscopic physics. The observability of many phenomena specific to this field relies on a long enough phase coherence time. 1 Amongst these are the weak localization correction to the conductance (WL), the universal conductance fluctuations (UCF), the Aharonov-Bohm (AB) effect, persistent currents in rings, the proximity effect near the interface between a superconductor and a normal metal, and others. Hence it is crucial to find out what mechanisms limit the quantum coherence of electrons.In metallic thin films, at low temperature, electrons experience mostly elastic collisions from sample boundaries, defects of the ion lattice and static impurities in the metal. These collisions do not destroy the quantum coherence of electrons. Instead they can be pictured as resulting from a static potential on which the diffusivelike electronic quantum states are built.What limits the quantum coherence of electrons are inelastic collisions. These are collisions with other electrons through the screened Coulomb interaction, with phonons, and also with extrinsic sources such as magnetic impurities or two level systems in the metal. Whereas above about 1 K electron-phonon interactions are known to be the dominant source of decoherence, 2 electron-electron interactions are expected to be the leading inelastic process at lower temperatures in samples without extrinsic sources of decoherence. 3 The theory of electron-electron interactions in the diffusive regime was worked out in the early 1980's (for a review see 4 ). It predicts a power law divergence of τ φ when the temperature T goes to zero....

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Section: Appendix C: Magnetic Field Dependence Of Spin-flip Scatmentioning

confidence: 57%

Section: Test Of the Magnetic Impurity Hypothesis: Probing τ φ (B)mentioning

confidence: 99%

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Dephasing of electrons in mesoscopic metal wires

et al. 2003

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“…Previous studies of EDLT-STO systems have shown Kondo effect at n > 6 * 10 13 with T K > 10 K [7,21]. At our lower carrier density, we might expect much lower T K , so our entire experimental temperature range could be T K , a regime in which magnetic impurities are predicted [22,23] and experimentally demonstrated [24,25] to yield constant-in-temperature dephasing.…”

mentioning

confidence: 98%

Universal conductance fluctuations in electrolyte-gated SrTiO3 nanostructures

Stanwyck¹,

Gallagher²,

Williams³

et al. 2013

Applied Physics Letters

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We report low-temperature magnetoconductance measurements of a patterned two-dimensional electron system (2DES) at the surface of strontium titanate, gated by an ionic liquid electrolyte. We observe universal conductance fluctuations, a signature of phase-coherent transport in mesoscopic devices. From the universal conductance fluctuations we extract an electron dephasing rate linear in temperature, characteristic of electron-electron interaction in a disordered conductor. Furthermore, the dephasing rate has a temperature-independent offset, suggestive of unscreened local magnetic moments in the sample.Strontium titanate (STO) has been the subject of a resurgence of experimental interest, mainly because of the recent ability to create STO-based materials with electrons confined in one and two spatial dimensions [1]. STO is also known to host a wide variety of electronic ground states determined by the density of electrons. These two aspects combine to create a promising system for studying nanoscale electronics where the interactions between electrons can be controlled simply by a gate voltage. Two-dimensional electron systems in STO have primarily been created in three different ways: growing a polar overlayer, usually lanthanum aluminate(LAO), to create a heterointerface[2], δ-doping with Nb or La [3,4], or with an electrolyte gate in an electric double-layer transistor (EDLT) configuration [5][6][7]. Low-temperature transport in these systems has revealed a wide variety of electronic ground states. Undoped STO is an insulator, but at ∼1x10 13 cm −2 the system becomes a metal. At higher densities (∼3x10 13 cm −2 ) -still much lower than typical BCS superconductors -the system becomes a two-dimensional superconductor. Early evidence suggests that the entrance into a superconducting state is a Berezinskii-KosterlitzThouless transition [8]. At even higher densities, a ferromagnetic phase appears to exist [9,10] and may even coexist with superconductivity [11][12][13].The handful of experiments on the quantum transport properties of two-dimensional electrons in STO have thus far focused on locally patterned LAO/STO, and have produced several interesting observations. The Rashba spin-orbit interaction -extracted from weak antilocalization measurements -is relatively large and tunable by application of a gate voltage. Further increases of the spinorbit strength have been linked to quantum critical points in the system [14,15]. Universal conductance fluctuations (UCF) corresponding to phase coherence lengths of several microns have recently been observed in LAO/STO microstructures [16]. Recently, conductive atomic force microscope tips have been used to create nanoscale conduction paths at the LAO/STO interface [17,18].In contrast, in electrolyte-gated STO some of the most basic properties of the quantum transport have yet to be investigated. In this work, we apply the EDLT technique to an undoped STO sample with nanopatterned metallic gates to study STO 2DESs with lateral confinement on the hundred-nanometer scale. ...

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“…Interestingly, non-universal value of α for the single diffusion mode resembles non-universal weak localization correction in a metal with partially polarized magnetic impurities when the rotational symmetry is broken. 38 It is important, however, to keep in mind that as temperature is decreased, one may expect a crossover behavior from α ∼ 3/2, when τ −1 φ ∼ 4eDB γ to α ∼ 1/2 for τ −1 φ 4eDB γ , see Fig. 2.…”

Section: B Wal Correction To Conductivitymentioning

confidence: 99%

Nonuniversal weak antilocalization effect in cubic topological Kondo insulators

et al. 2015

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We study the quantum correction to conductivity on the surface of cubic topological Kondo insulators with multiple Dirac bands. We consider the model of time-reversal invariant disorder which induces the scattering of the electrons within the Dirac bands as well as between the bands. When only intraband scattering is present we find three long-range diffusion modes leading to weak antilocalization correction to conductivity which remains independent of the microscopic details such as Fermi velocities and relaxation times. Interband scattering gaps out two diffusion modes leaving only one long-range mode. We find that depending on the value of the phase coherence time, either three or only one long-range diffusion modes contribute to weak localization correction rendering the quantum correction to conductivity non-universal. We provide an interpretation for the results of the recent transport experiments on samarium hexaboride where weak antilocalization has been observed.

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Conductance of mesoscopic systems with magnetic impurities

Cited by 57 publications

References 35 publications

Dephasing of electrons in mesoscopic metal wires

Dephasing of electrons in mesoscopic metal wires

Universal conductance fluctuations in electrolyte-gated SrTiO3 nanostructures

Nonuniversal weak antilocalization effect in cubic topological Kondo insulators

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